Op-ed | Incredible Shrinking Spacecraft
Often the focus of NASA and other space agencies is the large, big-ticket flight projects. This is natural and understandable because of the important role played by so-called flagship missions. It is also natural because of the budgetary impacts of even the slightest disruption in the programs at the large-class end of the flight mission spectrum.
On the other hand, it is also very important to focus attention on the smaller end of the flight program spectrum as well. Especially in a time of budgetary constraints, a highly productive and immensely beneficial advantage can be gained by relying on smaller-end missions. Moreover, because these budgets are small and projects are nimble, this can be done at quite modest cost and low risk to the success of the overall program.
These smaller spacecraft take advantage of the miniaturization of spacecraft parts that has been occurring in off-the-shelf components. A smartphone today has more computer power than the computers that were used on the original space shuttles, and those shuttle computers were not even radiation hardened.
Breakthrough research in space and Earth science is enabled by research platforms of a variety of sizes and with a range of functions. While $1 billion-scale strategic missions with 100-kilogram payloads can enable new measurements that would otherwise not be possible, it is clear that leading-edge research is possible with smaller-scale missions and spacecraft.
In particular, the study of the sun-Earth system requires multipoint observations to develop understanding of the coupling between disparate regions and to resolve temporal and spatial ambiguities that limit scientific understanding. Earth science has a variety of spatial and temporal requirements with a desire for polar orbits to get coverage of the entire planet. For example, studying phytoplankton in tidal areas would greatly benefit from multiple measurements throughout a single day.
In 2012, the National Research Council (NRC) of the U.S. National Academies released the report “Solar and Space Physics: A Science for a Technological Society.” That report from the NRC Committee on a Decadal Strategy for Solar and Space Physics (Heliophysics) was the second NRC decadal survey in solar and space physics. The report outlined programs, initiatives and investments in the field that would promote fundamental advances in scientific knowledge of the space environment — from the interior of the sun, to the atmosphere of Earth, to “space weather.” Considering scientific value, urgency, cost, risk and technical readiness, the report identified the highest-priority targets in the period 2013-2022.
A key development that was identified in the decadal survey is the realization of a new experimental capability for very small spacecraft. These spacecraft can act as stand-alone measurement platforms or can be integrated into a greater whole. They may be enabled by innovations in miniature, low-power, highly integrated electronics and micro- and nano-scale manufacturing techniques, novel approaches in robotics and system designs, and they provide potentially revolutionary approaches to experimental space and Earth science. For example, small, low-cost satellites may be deployed into regions where satellite lifetimes are short but where important, but poorly characterized, interactions take place. Operation of miniaturized avionics and instrumentation in high-radiation environments both spurs technological development and provides valuable space weather knowledge.
Experiments on very small spacecraft are also having an important educational impact. As part of the decadal survey’s evaluation of the workforce for solar and space physics, graduate students at National Science Foundation summer workshops were interviewed. These interviews indicated that the opportunity to work on space projects that could produce real results within the timeframe of a graduate career were a great attraction to the field. NSF’s cubesat initiative promotes science done by very small satellites and provides prime educational opportunities for young experimenters and engineers. The education and training value of these programs has been strongly recognized by the university research community, itself an argument for an increased launch cadence beyond the current roughly one per year. The initiative is also starting to bear fruit with respect to the novel scientific data these space systems have generated. As this program grows, it is critical to develop best-in-class educational programs and track the impacts of investments in these potentially game-changing assets and to continue to interpret the new science these new platforms produce.
We can speak from the experience at the Laboratory for Atmospheric and Space Physics that cubesats can make large science contributions. The Colorado Student Space Weather Experiment (CSSWE) was supported by NSF and was launched just about two weeks after the major NASA Van Allen Probes mission. The three-unit CSSWE cubesat began science operations in 2012 and operated very successfully for 2.5 years. The low-altitude data from the CSSWE investigation was the perfect complement to the data taken at high altitudes by the sophisticated Van Allen Probes instruments. The CSSWE team worked closely with the Van Allen Probes to produce numerous high-quality scientific publications. As one prominent example, the CSSWE data were featured in the 2014 publication for the journal Nature in which we reported the fascinating “Impenetrable Barrier” for ultra-relativistic electrons in Earth’s Van Allen belts.
To enable future missions it would be wise to accelerate the development of spacecraft technologies for supporting small satellites, including constellation operations and inter-spacecraft coordination. Also useful would be investigating systems engineering trades for designing a large constellation of small, scientific satellites, including balancing the risk of using modern, low-power electronics in space versus spacecraft lifetime.
Central to all of this, of course, is affordable access to space. NASA currently continues to place heavy emphasis on International Space Station resupply activities. The focus of launch suppliers on large launch vehicles tends to create a lopsided access to space geared toward the very large payloads. In fact, recent actions by major launch providers have left mainly secondary payload opportunities, such as payload adaptor rings and custom shared rides that provide few options necessary for some of the orbits and programs described here.
Even in fiscally challenging times, it is possible to have a vibrant, exciting and robust space flight program built around smaller, less-costly orbital, suborbital and ground-based systems. The 2013-2022 decadal survey for solar and space physics lays out an approach based partially upon this strategic pillar. Not every science goal of the nation can be accomplished on the basis of small satellites, but a great deal can be achieved by investing wisely in the realm of modest-sized systems. Today’s fiscal climate suggests that now is the time to move to this paradigm. Making the small end more vibrant can have immense benefits now and into the future.
Daniel N. Baker is director of the Laboratory for Atmospheric and Space Physics at the University of Colorado, Boulder. Mary L. Cleave is an environmental engineer and a former NASA astronaut and manager.